Tests and diagnosis

During the physical exam, your doctor may examine your joints for signs of inflammation such as swelling, warmth and tenderness. Your spine and affected joints may be assessed for range of motion. Your doctor might also check your eyes for inflammation and your skin for rashes.

Blood tests

Your doctor might recommend that a sample of your blood be tested for:

Evidence of past or present infections

Signs of inflammation

Antibodies associated with other types of arthritis

A genetic marker linked to reactive arthritis

Joint fluid tests

Your doctor may use a needle to withdraw a sample of fluid from within an affected joint. This fluid will be tested for:

White blood cell count. If the joint fluid has an increased number of white blood cells, it may indicate inflammation or an infection.

Infections. If your joint fluid contains bacteria, you may have septic arthritis, which can result in severe joint damage.

Crystals. If uric acid crystals are found in your joint fluid, you may have gout. This very painful type of arthritis often affects the big toe.

Imaging tests

X-rays of your low back, pelvis and joints can indicate whether you have any of the characteristic signs of reactive arthritis. X-rays can also rule out other types of arthritis.

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